﻿using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;

namespace Framework.Infrastructure
{
    public class FastInvoke
    {
        public delegate object FastInvokeHandler(object target, object[] paramters);
        static Hashtable FastInvokeHandlers = new Hashtable();

        public static FastInvokeHandler GetMethodInvoker(MethodInfo methodInfo)
        {
            FastInvokeHandler invoder = FastInvokeHandlers[methodInfo] as FastInvokeHandler;
            if (invoder == null)
            {
                lock (FastInvokeHandlers)
                {
                    invoder = FastInvokeHandlers[methodInfo] as FastInvokeHandler;
                    if (invoder == null)
                    {
                        DynamicMethod dynamicMethod = new DynamicMethod(string.Empty, typeof(object), new Type[] { typeof(object), typeof(object[]) }, methodInfo.DeclaringType.Module, true);
                        ILGenerator il = dynamicMethod.GetILGenerator();
                        ParameterInfo[] ps = methodInfo.GetParameters();
                        Type[] paramTypes = new Type[ps.Length];
                        for (int i = 0; i < paramTypes.Length; i++)
                        {
                            if (ps[i].ParameterType.IsByRef)
                                paramTypes[i] = ps[i].ParameterType.GetElementType();
                            else
                                paramTypes[i] = ps[i].ParameterType;
                        }
                        LocalBuilder[] locals = new LocalBuilder[paramTypes.Length];

                        for (int i = 0; i < paramTypes.Length; i++)
                        {
                            locals[i] = il.DeclareLocal(paramTypes[i], true);
                        }
                        for (int i = 0; i < paramTypes.Length; i++)
                        {
                            il.Emit(OpCodes.Ldarg_1);
                            EmitFastInt(il, i);
                            il.Emit(OpCodes.Ldelem_Ref);
                            EmitCastToReference(il, paramTypes[i]);
                            il.Emit(OpCodes.Stloc, locals[i]);
                        }
                        if (!methodInfo.IsStatic)
                        {
                            il.Emit(OpCodes.Ldarg_0);
                        }
                        for (int i = 0; i < paramTypes.Length; i++)
                        {
                            if (ps[i].ParameterType.IsByRef)
                                il.Emit(OpCodes.Ldloca_S, locals[i]);
                            else
                                il.Emit(OpCodes.Ldloc, locals[i]);
                        }
                        if (methodInfo.IsStatic)
                            il.EmitCall(OpCodes.Call, methodInfo, null);
                        else
                            il.EmitCall(OpCodes.Callvirt, methodInfo, null);
                        if (methodInfo.ReturnType == typeof(void))
                            il.Emit(OpCodes.Ldnull);
                        else
                            EmitBoxIfNeeded(il, methodInfo.ReturnType);

                        for (int i = 0; i < paramTypes.Length; i++)
                        {
                            if (ps[i].ParameterType.IsByRef)
                            {
                                il.Emit(OpCodes.Ldarg_1);
                                EmitFastInt(il, i);
                                il.Emit(OpCodes.Ldloc, locals[i]);
                                if (locals[i].LocalType.IsValueType)
                                    il.Emit(OpCodes.Box, locals[i].LocalType);
                                il.Emit(OpCodes.Stelem_Ref);
                            }
                        }

                        il.Emit(OpCodes.Ret);
                        invoder = (FastInvokeHandler)dynamicMethod.CreateDelegate(typeof(FastInvokeHandler));
                        FastInvokeHandlers.Add(methodInfo, invoder);
                    }
                }
            }
            return invoder;
        }

        private static void EmitBoxIfNeeded(ILGenerator il, System.Type type)
        {
            if (type.IsValueType)
            {
                il.Emit(OpCodes.Box, type);
            }
        }

        private static void EmitFastInt(ILGenerator il, int value)
        {
            switch (value)
            {
                case -1:
                    il.Emit(OpCodes.Ldc_I4_M1);
                    return;
                case 0:
                    il.Emit(OpCodes.Ldc_I4_0);
                    return;
                case 1:
                    il.Emit(OpCodes.Ldc_I4_1);
                    return;
                case 2:
                    il.Emit(OpCodes.Ldc_I4_2);
                    return;
                case 3:
                    il.Emit(OpCodes.Ldc_I4_3);
                    return;
                case 4:
                    il.Emit(OpCodes.Ldc_I4_4);
                    return;
                case 5:
                    il.Emit(OpCodes.Ldc_I4_5);
                    return;
                case 6:
                    il.Emit(OpCodes.Ldc_I4_6);
                    return;
                case 7:
                    il.Emit(OpCodes.Ldc_I4_7);
                    return;
                case 8:
                    il.Emit(OpCodes.Ldc_I4_8);
                    return;
            }

            if (value > -129 && value < 128)
            {
                il.Emit(OpCodes.Ldc_I4_S, (SByte)value);
            }
            else
            {
                il.Emit(OpCodes.Ldc_I4, value);
            }
        }

        private static void EmitCastToReference(ILGenerator il, System.Type type)
        {
            if (type.IsValueType)
            {
                il.Emit(OpCodes.Unbox_Any, type);
            }
            else
            {
                il.Emit(OpCodes.Castclass, type);
            }
        }

    }
}
